High-speed circuitry, such as that used in modem microprocessors, demands the presence of a high-performance power supply. That is, voltage regulators that supply power to a central processing unit (CPU), for example, must provide high-speed dynamic response and tight voltage tolerance. Essentially, a responsive power source (e.g., a local switching regulator), along with low impedance power delivery and decoupling are required. Unfortunately, the speed of voltage regulators available today continues to be constrained by power field effect transistor (FET) device technology. The presence of decoupling capacitors, device packaging, sockets, and circuit boards also serves to limit the designer's ability to deliver low impedance power.
For example, in the case of a CPU, power is typically applied to one side of a multi-sided CPU socket attached to a motherboard. Even if a state of the art voltage regulator and decoupling capacitors are used, large voltage droops may appear at the socket pins, as well as unbalanced current distribution. Ultimately, CPU socket power delivery capability is limited, the performance of the CPU may be affected, and the socket life may be shortened.
This can be easily seen with reference to prior art FIG. 1, illustrating a single voltage regulator (VR) which provides power to a socketed CPU. For convenience, the socket sides can be labeled as North “N” and South “S”. The VR 101 powers the socketed CPU 102 by way of the socket pins 103 (on the N side of the socket) and socket pins 104 (on the S side of the socket), as well as by using the motherboard traces 105. Such prior art power delivery systems are subject to voltage droops on the order of 10%, or greater, as the CPU 102 operates and current demands rapidly change. Because the current required by the CPU 102 flows through unequal impedances (since the impedance of the motherboard traces 105 is added to that of the S socket pins 104, and not to the impedance of the N socket pins 103), the current from the VR 101 is not shared equally between the N side socket pins and the S side socket pins. The increased impedance provided by the motherboard traces 105 also tends to increase the voltage droop of the VR 101.
Thus, there is a need to provide a power supply method and apparatus which minimizes the inequitable distribution of current of the prior art, increasing CPU socket life. Such a method and apparatus should also operate to increase the ability of voltage regulators to provide a tightly controlled source of voltage, reducing the amount of droop encountered when large quantities of current must be delivered quickly.